Such motors are generally controlled by means of a static converter that is connected to a DC voltage source and that delivers voltages for each of the phases of the motor, e.g. by means of power transistors that are controlled to switch on and off in a manner that is servo-controlled to the angular position of the rotor of the motor. For this purpose, the motor is generally fitted with means for measuring its angular position, which means deliver a signal that is representative of said position, the signal being used by the static converter to switch the power transistors on and off so as to perform the automatic synchronous switching function that is performed by the commutator in a motor with brushes.
It is also appropriate to adapt the voltage that is delivered to the level of power or torque that is required. For this purpose, the static converter is generally controlled to vary the voltage delivered to the motor as a function of the mechanical power or the torque that it is supposed to deliver. Thus, in response to a power or torque setpoint, the static converter sends a variable voltage to the motor so as to enable the motor to develop the requested power or torque. For this purpose, various voltage-varying methods are known, such as for example pulse width modulation (PWM).
Control arrangements are also known that include a static contactor associated with an angle position sensor for controlling power transistors, the static contactor then not performing the voltage-varying function of static converters, but only the synchronizing function. The voltage is varied by means of an upstream DC/DC converter that delivers a variable DC voltage to the static contactor.